System incorporating an insole pressure sensor and personal annunciator for use in gait assistive therapy

ABSTRACT

A system designed to assist with the therapeutic treatment of subjects who have difficulty in walking, specifically those with a lack of sensation due to nerve damage or amputation, who are unable to tell when the foot makes contact with the floor. The system consists of: 1. A removable insole placed inside the shoe which proportionally senses touchdown. 2. A miniature wireless transmitter which can be worn unobtrusively on the shoe. 3. A miniature wireless receiver with tone generator which feeds an earpiece worn by the user. 4. A separate wireless receiver used by the therapist to monitor the same signal received by the user, in order to facilitate initial set-up and adjustments.

BACKGROUND OF THE INVENTION

One of the problems associated with hip, knee and foot surgery is a loss of sensation in the affected limb. Although the limb may be physically whole and the associated muscles are controllable, visual confirmation of contact between the foot and the ground is necessary. Visual confirmation is also essential in the case of amputation of the limb and certain degenerative conditions due to medical circumstances, eg: diabetes, frostbite, obesity.

Those without sensation in the lower limbs also experience difficulty in operating machinery where vision has to be concentrated on the machine in use, eg: motor vehicle, yard equipment. Activities such as negotiating steps and ladders, stepping backwards, responding to moving objects (eg: crossing a road in traffic), walking in darkness or on uneven surfaces and carrying large objects are made much more difficult without sensory feedback from the feet.

Quite often, the post=surgical medication given, reduces the patients ability to concentrate visually on the movement of the feet.

There are also certain medical conditions which preclude a patient from looking downwards to check each step taken, eg: progressive supranuclear palsy (PSP) and certain balance disorders.

Although there are devices available which will indicate pressure on the foot, they are designed for gait corrective therapy in a clinical environment and are not intended for everyday use.

In reality, the only existent remedy for those affected, is to use a cane, or, in the worst cases a wheelchair.

BRIEF SUMMARY OF THE INVENTION

When using the system described in this invention, the subject receives an audible or sensory signal indicating that the foot is in contact with the ground.

This signal is immediately assimilated by the brain, replacing the missing sensory feedback from the damaged nerves in the foot. This removes the need for visual confirmation, thereby assisting the user to walk normally.

BRIEF DESCRIPTION OF SUBMITTED DRAWINGS

1. A block diagram of the complete system with audible signal output.

2. A block diagram of the complete system with vibrating signal output.

3. A detailed diagram of the construction of the insole pressure sensor.

DETAILED DESCRIPTION OF THE INVENTION

The invention consists of the following elements:

-   -   1. Foot pressure sensor     -   2. Adjustable threshold sensor interface     -   3. Addressable wireless data transmitter.     -   4. Addressable wireless data receiver.     -   5. User interface.     -   6. Therapy Clinic set-up receiver.         1. The insole pressure sensor is a composite foam sandwich,         consisting of three layers:     -   a.) The lower layer of foam has areas of conductive fabric tape         attached to the upper side corresponding to the separate areas         of the sole of the foot to be monitored.     -   b.) The middle layer of foam has punched holes in a grid pattern         in each of the areas of the foot to be monitored, into which         cores of conductive foam have been inserted.     -   c.) The upper layer of foam is a mirror image of the lower         layer, with the areas of conductive fabric attached to the lower         side of the foam.

Electrical connecting cables are attached to each area of conducting fabric, using conductive silicone glue, and are led out from the area on the inside of the arch of the foot.

The sandwich is then glued together to create a one-piece flexible shoe insert, which can be trimmed to fit the patients shoe size.

The insole can simply be inverted for use in either left or right shoe.

2. Each pair of connecting wires from the insole is led to an electronic circuit comprised of an adjustable voltage divider network and a comparator.

The voltage divider network can be adjusted to prevent false signals which may arise from the normal pressure exerted by the foot on the insole when not in contact with the ground.

The pressure required to trigger the comparator can be set to accomodate the loading requirements of individual therapy.

When the pressure on each area of the insole reaches the pre-set level, the comparator changes state and provides a digital output.

3. The digital output from each comparator is encoded and fed to a commercially available addressable miniature wireless transmitter, which can be located in the same enclosure as the comparator circuitry.

The addressable feature of the transmitter is to ensure exclusivity between individual systems.

The transmitter enclosure is small enough to be worn unobtrusively on the side of the shoe or on the users ankle.

4. The data from the transmitter is received by a commercially available addressable miniature wireless receiver and is decoded.

5. Each output from the decoder, corresponding to the separate areas of the insole, is fed to a ‘one-shot’ oscillator which provides a pulse, the length of which can be adjusted to suit the user.

Each ‘one-shot’ pulse triggers an audio oscillator, the frequency and amplitude of which can be adjusted to suit the user.

The outputs from each audio oscillator are combined and fed to an earpiece worn by the user.

Alternatively, the outputs from the ‘one-shot’ oscillators can each be fed to a driver circuit which activates a vibrating alert such as used in a mobile pager, to provide a sensory indication of foot ‘touchdown’.

The vibrating alerts can be worn on any part of the body to suit the user.

6. To assist with initial set-up and adjustment of each users system, the therapist is equipped with a similar addressable receiver, the outputs from which will provide audible signals from a loudspeaker and visual signals from indicator lights which correspond to each of the areas of the insole pressure sensor. 

1. A method for electrically sensing that loads are being exerted on certain areas of the foot, both statically and during ambulation.
 2. A method for adjusting the sensitivity of a data switch, whereby the raw information from the load sensors in claim (1) can be assigned preset thresholds.
 3. A means of transmitting said load sensor data to a receiver worn by the user, and of converting that received data to a signal that the user can sense. 